A cytosolic, galphaq- and betagamma-insensitive splice variant of phospholipase C-beta4.
Phospholipase C (PLC)-beta4 has been considered to be a mammalian homolog of the NorpA PLC, which is responsible for visual signal transduction in Drosophila. We reported previously the cloning of a cDNA encoding rat phospholipase C-beta4 (PLC-beta4) (Kim, M. J., Bahk, Y. Y., Min, D. S., Lee, S. J., Ryu, S. H., and Suh, P.-G. (1993) Biochem. Biophys. Res. Commun. 194, 706-712). We report now the isolation and characterization of a splice variant (PLC-beta4b). PLC-beta4b is identical to the 130-kDa PLC-beta4 (PLC-beta4a) except that the carboxyl-terminal 162 amino acids of PLC-beta4a are replaced by 10 distinct amino acids. The existence of PLC-beta4b transcripts in the rat brain was demonstrated by reverse transcription-polymerase chain reaction analysis. Immunological analysis using polyclonal antibody specific for PLC-beta4b revealed that this splice variant exists in rat brain cytosol. To investigate functional differences between the two forms of PLC-beta4, transient expression studies in COS-7 cells were conducted. We found that PLC-beta4a was localized mainly in the particulate fraction of the cell, and it could be activated by Galphaq, whereas PLC-beta4b was localized exclusively in the soluble fraction, and it could not be activated by Galphaq. In addition, both PLC-beta4a and PLC-beta4b were not activated by G-protein betagamma-subunits purified from rat brain. These results suggest that PLC-beta4b may be regulated by a mechanism different from that of PLC-beta4a, and therefore it may play a distinct role in PLC-mediated signal transduction.
Kim
M J
MJ
Department of Life Science, Pohang University of Science and Technology, Pohang, 790-784, South Korea.
Min
D S
DS
Ryu
S H
SH
Suh
P G
PG
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D001921:Brain / Q000201:enzymology; D019556:COS Cells; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology*; D018076:DNA, Complementary; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D054799:Phospholipase C beta; D016133:Polymerase Chain Reaction; D051381:Rats; D014158:Transcription, Genetic; D010738:Type C Phospholipases / Q000235:genetics* / Q000378:metabolism
D018076:DNA, Complementary; D007527:Isoenzymes; D010738:Type C Phospholipases; D054799:Phospholipase C beta; C518044:Plcb4 protein, rat; D019204:GTP-Binding Proteins